EP0577981B1 - Head for a medical or dental handpiece comprising an oscillating treatment tool - Google Patents

Description

The invention relates to a handpiece head according to the preamble of claim 1 or 2. The features of the preamble of Claims 1 and 2 are known from WO-A-90/00885.

In addition to rotating treatment tools, there are also every now and then Movable treatment tools, i.e. a movement stroke, e.g. with a flat or leaf-shaped Cross-section. With such a treatment tool, it can a tool for working or cleaning the teeth act.

Such a handpiece head is described in US-A-3,552,022. In this known embodiment, this is Treatment tool can be clamped in a lifting sleeve in bearings is slidable in the handpiece head and can be moved longitudinally by an eccentric of a drive shaft which is in the present embodiment as an angular head extends at right angles to the lifting sleeve. The exenter holds in a circumferential annular groove of the lifting sleeve. This makes them Lifting sleeve and the treatment tool even during operation freely rotatable, and therefore it is in this configuration only possible over the entire area with the existing leaf-shaped longitudinally movable treatment tool, in particular a flat file to work. Once the treating Person turns the handpiece slightly to produce a torque to exercise on the treatment tool, the latter also turns, and that is why certain tooth formings cannot be made precisely because the treatment tool itself always adapts to the surface to be worked.

Would you be a drive connection to the treatment tool create, in which the treatment tool can be moved longitudinally but is non-rotatably mounted in the handpiece head, a torque could be applied to the treatment tool with the handpiece can be exercised and could thus also certain Forming work on the tooth or between teeth would, however, then there would be the danger that with the aforementioned torque on a considerable leverage the tooth is exerted and this is damaged could. An example of this would be if one between two Teeth-fitting flat file would be rotated. The flat file would spread its teeth due to their rotation, whereby It should be noted that due to the length of the Handpiece given active lever arm a considerable Torque can be transmitted with the treatment tool can cause damage to the tooth.

In order to avoid the difficulty described above, according to WO / 90/00885 for a handpiece head of the type mentioned Art has already been proposed by means of the handpiece of the treatment tool torque that can be transmitted to the tooth to limit. 1, 1A and 2 of this document an angular handpiece head is provided, the treatment tool has a mounting shaft with which it from the processing side of the handpiece head into one in its longitudinal direction back and forth sliding sleeve in Handpiece head can be inserted into the fastening shaft in the inserted position by a form-fitting effective Positioning clutch is positioned.

There are several positioning coupling positions in the form of several recesses at the lower edge of the lifting sleeve in which a coupling pin at the lower end of the Fastening shaft of the treatment tool either through Insertable from below and by pulling downwards how can be brought out. 2 This known handpiece head is an overturn protection device assigned in the form of an overspeed clutch one or more arranged around the circumference axial and trough-shaped recesses and a coupling body in the form of a ball in a recess in the inner wall of the housing is arranged so that it in protrudes the interior and thus into one of the gutter-shaped Binding coupling recesses. The lifting sleeve consists of a Plastic material with a certain flexibility or flexibility. If with the handpiece using the treatment tool transfer a torque to the tooth to be treated that is greater than a certain torque, then give the existing between the coupling recesses Web walls after, so that the formed in the manner described above Overspeed clutch is overturned. This is supposed to cause damage of the tooth can be avoided. This known configuration is disadvantageous for several reasons. It can be the torque at which the overturning clutch should overturn not determine exactly, so that of the strength of the material dependent different overtorques specified are where the tooth is already damaged. Furthermore, it can be expected that after an overspeed changed resistance values of the material, so that with wear of the overturn coupling is to be expected. Furthermore the positioning coupling can only be handled unfriendly operate, the treatment tool directly with the Fingers must be grasped, which is the sharpness of the treatment tool impaired and also for hygienic reasons is very worrying. 3 to 18 is the treatment tool with a fastening and drive shaft integrally formed. With such a configuration the positioning coupling and the overturning coupling between the housing and the treatment tool directly effective. 15 are not only those in the upper region of the Fastening shaft of the treatment tool arranged Coupling recesses of the positioning clutch but also a single coupling recess in the lower area of the fastening shaft executed in the sense of a longitudinal channel, so that ensures the longitudinal displaceability of the treatment tool is.

The invention has for its object a handpiece head according to that described in the preamble of claim 1 or 2 Kind in such a way that on the one hand the functional reliability with a constant overturn trigger torque and / or on the other hand an easy-to-use rotary setting of the treatment tool is possible. Also lies special embodiments the invention has the object of desired triggering moments the overturning coupling and / or positions of the positioning coupling to be easy to handle and therefore the Handpiece head for different types of treatment or treatment criticism to be able to adapt. It should go further it can also be possible to lock the overturning clutch can, so that even large torques with the treatment tool can be generated if e.g. treating this required.

The object underlying the invention is achieved by Features of claim 1 or 2 solved.

In the handpiece head according to the invention is a easy-to-use rotary position setting ensures the treatment tool from direct manual Access is free and therefore pollution and Hygienic impairment of the tool when setting the rotational position is omitted. In addition, the treatment tool without its longitudinal displacement and without a solution its drive connection in an optional rotational position adjustable.

With the configuration according to the invention according to claim 2 a reliable overturn protection device has been reached, where the triggering of the overturning clutch is both is exactly predeterminable as well as feasible even after a longer lifespan. It won't just be a particular one leaf-shaped treatment tool against overload protected, but it also protects the teeth from overload protected, e.g. when a particular leaf-shaped Treatment tool through a gap between two teeth must be passed through or a jammed in the gap Treatment tool must be pulled out.

The positioning clutch and the overturning clutch can be adjusted by one and the same clutch can be formed. This will not only reduce manufacturing costs very reduced, resulting in lower manufacturing costs leads, but it is also the operating effort less, and also this configuration leads to a small design because there is only one coupling.

The handpiece head does not have an adjustment device, which is easy to use Adjustment of the functional criteria either the positioning coupling or the overturning coupling (if so available) or both couplings. It leaves the engagement or disengagement torque of the respective clutch and thus selectively set the overtorque and to each adjust existing treatment criteria. It is possible, the overturning coupling and / or the positioning coupling to put out of function or the overturning clutch too freeze to e.g. on the treatment tool below Considering special treatment criteria a big one To be able to transfer the rotary instrument in a targeted manner.

Features are contained in the subclaims which are used for problem solving contribute to a rotational position adjustment in small Turn stages enable to stable and reliable Configurations lead long life and also simple and inexpensive to manufacture and small designs pretend.

Fig. 1

einen erfindungsgemäßen Handstückkopf in der Seitenansicht;

Fig. 2

den Handstückkopf im vertikalen Längsschnitt und in vergrößerter Darstellung;

Fig. 3

ein Mitnehmerteil des Handstückkopfs im vertikalen Schnitt;

Fig. 4

das Mitnehmerteil in der Unteransicht;

Fig. 5

das Mitnehmerteil in der Seitenansicht;

Fig. 6

den wesentlichen Teil eines abgewandelten Handstückkopfs im vertikalen Längsschnitt und in vergrößerter Darstellung in einer ersten Funktionsstellung;

Fig. 7

den Handstückkopf nach Fig. 6 in einer zweiten Funktionsstellung;

Fig. 8

den Teilschnitt VIII-VIII in Fig. 6.

The invention and further advantages which can be achieved by means of a preferred exemplary embodiment and a drawing are explained in more detail below. Show it

Fig. 1

a handpiece head according to the invention in side view;

Fig. 2

the handpiece head in vertical longitudinal section and in an enlarged view;

Fig. 3

a driver part of the handpiece head in vertical section;

Fig. 4

the driver part in the bottom view;

Fig. 5

the driver part in the side view;

Fig. 6

the essential part of a modified handpiece head in vertical longitudinal section and in an enlarged view in a first functional position;

Fig. 7

6 in a second functional position;

Fig. 8

the partial section VIII-VIII in Fig. 6.

In the present exemplary embodiment, the handpiece head 1 only part of a handpiece 2, which is only partially indicated is shown. The handpiece head 1 consists of an angular head housing 3, the rear housing section 3a in the state mounted on the handpiece 2, a front one Extension of the grip sleeve 2a of the handpiece 2 with a Longitudinal central axis 4 is.

As shown in FIG. 2 in particular, the angle head housing 3 an axial bearing bore in the area of its housing section 3a 5 on that going forward in a perpendicular to it bearing bore made in stages 6 flows. In the bearing bore 6 is a hollow cylindrical tappet sleeve 7 in its longitudinal direction, i.e. across the handpiece head 1, slidable back and forth a few millimeters rotatably mounted. In the cylindrical bore 8 of the tappet sleeve 7 is a machining tool shown in FIG. 1 9 with a cylindrical arranged along its central axis 9a Holding shaft 11 closing from the tool side insertable and clampable. The tool 9 is longitudinal oscillating mode of operation, it being the present Embodiment around a flat in cross section or sword-shaped tool 9 acts like a file with its broad and / or narrow sides during its lifting movement can be machined or - depending on the fineness - Can be smoothed or polished.

The tappet sleeve 7 has two one in its central region axially spaced flanges 12, between which formed a circumferential groove 13 of rectangular cross section is. In their on both sides of the flanges 12 End areas is the tappet sleeve 7 in plain bearing rings 14, 15 mounted in the area on both sides Bearing bore sections are arranged, at which Outside of each slide bearing ring 14, 15 each have a sealing ring 16 with an axially outward wiping lip is arranged.

The slide bearing remote from the tool is with its slide bearing ring 14 arranged in a socket 17 which is stepped into an outer screwed enlarged end portion of the bearing bore 6 (thread 18). The socket 17 also has one three-stage bore, with an inner bore section 17a, in which the plain bearing ring 14 is firmly inserted, one middle bore section 17b, in which a driving ring 21st is rotatably mounted with movement play and an outer Bore section 17c. The driver ring 21 has a Z-shaped Cross section on, being on the outer, tapered Ring section 21a on the inside diametrically opposite one another Driver pins 22 are integrally formed, the diametrically opposed to each other with little movement enclose radial slots 23 of the tappet sleeve 7, wherein the slots 23 open out axially at the end.

This results in a first coupling between the tappet sleeve 7 and the driving ring 21 or the flange 19 or the housing 9 created a longitudinal movement required for the stroke the tappet sleeve 7 allows, but rotating the tappet sleeve 7 prevented. The coupling pin or pins 22 and the slots 23 can also be arranged upside down.

On the flange 19 is a rotary flange 24 with little play rotatably mounted, the axially outside of Flange 19 is arranged and with its outer edge 25 the Flange 19 C-shaped overlaps and grips behind, which makes the rotary flange 24 on the flange 19 in the axial and radial directions is rotatably held. The rotary flange 24 has on the outer circumference to improve a grip strength grooves, webs or a Knurling on. In the inner wall of the rotary flange 24 or of the flange 19 are diametrically opposite one another axially and radially arranged slots 26 are provided in the the axially projecting driver pins with little play 22 enclose with their radially outer regions.

The plain bearing ring 14 and the driving ring 21 lie with End faces face each other, and they engage with each a toothing 27 arranged on these end faces into each other. Such a toothing is provided, the can be suppressed by rotating one part relative to the other part is. This is due to inclined flanks 27a of the toothing 27 possible, the inclination of the sloping flanks (see Fig. 5) to the maximum torque that the toothing 27 is to be transferred so that when exceeded this torque, the driver ring 21 axially outwards the tooth mesh is pushed out. This is the Driving ring 21 an axial freedom of movement between the Slide bearing ring 14 and the inner step surface 28 of the bush 17 provided. This freedom of movement 29 is axially through the step surface 28 of the socket 17 and the step surface 31 of the Driver ring 21 limited. The distance a between them is larger dimensioned as the height h of the toothing 27 and the height of one or more arranged in the freedom of movement 29 Wave springs 32 which axially engage the driving ring 21 in the toothing engagement preload elastically.

In the rotating flange 24 and in the flange 19, two are diametrically opposed to each other opposite one another, each of which can be brought into flight axial bores 33a, 33b are provided. Through the outer Bores 33a in the rotary flange 24 can pass through the pins a wrench, not shown, in the holes 33b are inserted for the purpose of screwing in or unscrewing the socket 17. The flange 19 and the rotary flange 24 are firmly connected and thus form a common Turned part.

In the present embodiment, the rotary flange 24 a coaxial hole 34 on the supply of cooling or Flushing liquid to the treatment tool through the plunger sleeve 7 by means of a feed device, not shown can serve.

In order to ensure the axial stroke movement of the tappet sleeve 7, a space is required on both sides of the flanges 12 and a corresponding length of the slots 23 so that the inner Driver pin 22 not against the inner slot ends bump.

For driving the plunger sleeve 7 is at the front end Drive shaft train of the handpiece 2 an eccentric cylindrical Drive pin 35 provided in the circumferential groove 13 borders with little movement. In the present The embodiment is a drive pin 35 supporting Drive shaft section 36 with a tooth coupling or Bevel gear 36 of a bevel gear at its rear end provided in a bearing sleeve 37, preferably in Plain bearings 37a is rotatably mounted, thereby a Drive cartridge 38 is formed. The drive cartridge 38 is seated in the bearing bore 5 and is radially screwed into it Fixing screw 39 secured in a radial Threaded hole 41 in the bearing sleeve 37 and in a so aligned hole 42 is screwed into the housing section 3a. The bearing sleeve 37 projects beyond the housing section 3a to the rear and forms a bearing journal with this rear section 38a by elastic and when pulling out latching connection 43 which can be pushed over from the handpiece 2 in the handpiece 2 is releasably fixable. The locking connection 43 can by at least one locking recess 44 in the lateral surface of the bearing pin 38a and a locking ball 45 may be formed radially displaceably mounted in the sleeve of the handpiece 2 and elastically biased into the recess 44 by a spring is.

With the above-described handpiece head 1, rotational position settings can optionally be made of the tool 9 with respect to the handpiece head 1 can be set independently of the respective stroke position of the tappet sleeve 7 or its drive. The rotary setting can be done in small steps, what due to the relatively small pitch of the toothing 27 is guaranteed. The toothing 27 forms a second detachable Coupling 46 between the tappet sleeve 7 or the driving ring 21 and the plain bearing ring 14, which are exceeded a predetermined torque automatically opens and automatically closes again. This makes it possible to Turning the rotary flange 24 in one or the other direction of rotation to set a desired rotational position of the tool 9. On the other hand, when a predetermined torque on the tool 9 is exceeded, the tappet sleeve 7 follows this Rotational stress automatically, the toothing 27 suppresses or overturned, i.e. like a ratchet lock drive works at idle. As a result, pressure loads or Damage to the teeth excluded from the handpiece 2 based on leverage effects arising from handling.

It is not necessary that the teeth 27 on both Gear parts must be fully trained. The function is also guaranteed if a part complete sprocket and theoretically only on the other part one, preferably two or more distributed over the circumference arranged teeth 27b are provided. In the present Three teeth 27b are arranged evenly distributed and preferably on the driving ring 21, as is Fig. 4 shows. On the plain bearing ring 14, however, is a full stand Gear ring with corresponding sloping flanks Teeth provided.

Depending on the type of dental treatment, it can be advantageous to use a tool 9 to work that up to a predetermined Torque is not rotatable or above this torque is not rotatable or work with a tool, that is easily or freely rotatable about its longitudinal central axis. This is made possible by the configuration according to FIGS. 6 to 8, at the same or comparable parts with the same Reference numerals are provided, and in the handpiece head 1 an adjustment device 51 is assigned, in the 6, the clutch 46 is engaged and thus the tool 9 is rotationally limited, and in whose other adjustment position according to FIG. 7 is the engagement bias the clutch 46 is reduced or completely canceled and thus the tool 9 is easily or freely rotatable. It is also possible, the adjustment device 51 a further adjustment position assign in which the torque at which the Clutch 46 can be pushed or turned, is very large, or cannot be overpressed or overturned in clutch 46 is.

The adjusting device 51 contains a according to FIGS. 6 to 8 Actuator with which one, here the rotationally fixed with Ram sleeve 7 connected coupling part disengageable and in the disengaged position can be fixed (not shown), or with which the engagement bias of clutch 46 is reduced or can be canceled entirely. In the present embodiment are of the comprehensive adjustment device 51 Modification of the flange 19 and the rotary flange 24 design affected. These parts are in the design 6 to 8 with the reference symbol a. In this variant, the flange 19a has its no inner flange on the outer end, but its inner wall is essentially cylindrical. In contrast, the rotary flange 24a on a coaxial inner ring projection 24b the inner end face of the axial spring, here wave springs 32, which bear the driving ring 21 with its teeth in preloads the clutch engagement position. In addition, the Rotary flange 24a axially displaceable relative to flange 19a, 6 in the inserted position according to FIG are axially compressed and thus an engagement preload is present, which corresponds to the embodiment 1 to 5, can be suppressed or not suppressed is. 7, in which the rotary flange 24a axially after the position shown in FIG. 6 shifted outside is the clutch engagement bias, here the wave springs 32, reduced or relaxed, see above that the plunger sleeve 7 is easily rotatable with the tool 9. It is possible to have another adjustment position for the rotary flange 24a to provide in which he on the position according to Fig. 6 is also shifted inwards, and in which the springs 32 and the toothing 27 are compressed so far, that the movable tooth or coupling part 21 does not evade capable and therefore the clutch 46 can not be suppressed or can be turned.

The displaceability of the rotary flange 24a on the flange 19a is made possible by an axial sliding bearing. In the The present embodiment overlaps the rotary flange 24a Flange 19a with a hollow cylindrical ring wall 24c around the axial displacement dimension m is longer than that effective flange 19a of the sleeve 17, the annular wall 24c has an inner shoulder 24d at its inner end which by moving against the flange 19a limited outside. The rotary flange 24 is thus capable of little Axial play on the peripheral surface of the flange 19a to slide. The adjusting device 51 is in the coupling position (Fig. 6) and in the quasi final coupling position (Fig. 7) each have an elastically pressable latching device 52, 53 assigned to an unintentional adjustment to avoid from the respective adjustment position. In the The present embodiment is the two latching devices 52, 53 assigned a common spring element, which on stationary part, here the flange 19a, is arranged and in Locking recesses 52a, 53a in the inner wall of the ring wall 24c can snap into place. The spring element 54 can 8 bent into a U-shape as shown in FIG Circumferential direction curved, preferably round in cross section Act spring wire in an approximately secantial slot 55 is received in the flange 19a and with its inner leg 54a is supported on the inner ring projection 24b and with its convex curved outer leg 54b into the recesses 52a, 53a can snap into place, preferably through annular locking grooves with a rounded cross-section in the inner wall the annular wall 24c are formed. As with the first 1 to 5 is in the second 6 to 8, the inner wall of the hollow cylindrical ring wall 24c through a thin sleeve with the Inner shoulder 24d formed which is fixed in the annular wall 24c sits, e.g. is pressed.

The above-described adjusting device 51 stands out through a simple, reliable and easy to use Construction. For an adjustment between the indented 6 and the quasi 7 only needs the user to grip the rotary flange 24a on its circumference and axially into the respective adjustment position or latching device 52 or 53 to move. Otherwise, the handpiece head 1 correspond to the configuration according to FIGS. 1 to 5. However, the adjustment device 51 according to the invention is not limited to a coupling 46 according to FIGS. 1 to 5. in the Within the scope of the invention it is possible to use the adjusting device 51 also another coupling between the tool holder, here the tappet sleeve 7, and the housing 3 or an attachment assign to the same.

The handpiece head 1 is in several aspects of the invention advantageous. One aspect is him with one equip functionally reliable overturn protection device, causing damage to the tooth to be machined as well of the treatment tool 9 can be avoided. At a Such a design of the handpiece head 1 can be a rotary handle for the treatment tool 9, here the rotary flange 24, omitted, or it can also be a rotational position adjusting device other configuration may be provided.

A second aspect of the invention is the handpiece head with an easy-to-use rotary position adjustment device for the treatment tool 9 equip. With this configuration, an overturn protection device could omitted (if not desired is), or it could also be an overturn protection device other type may be provided.

The positioning clutch and the over-rotation clutch can be made by one and the same Coupling be formed, the coupling of a suitable design can be.

One can continue Adjustment device 51 for the position setting device or positioning clutch and / or the overturn protection device or overturn coupling. With such a The handpiece head according to the invention can the positioning adjustment device or the overturn protection device omitted.

Claims (24)

1. Head (1) for a medical or dental handpiece (2), comprising a casing (3), in particular an angled casing, in which a treatment tool (9) is supported so as to be displaceable back and forth along its central axis (9a) and rotatable,
   wherein a rotary-position setting device for the treatment tool (9) is assigned to the handpiece head (1), said setting device comprising a positioning coupling (46) with two coupling parts (14, 21) interacting with one another,
   characterised in that

   a rotary-action member (24) for the treatment tool (9) which is manually accessible from outside is movably supported on or in the casing (3),

   in that the positioning coupling (46) is disposed in the casing (3) and is effective between the rotary-action member (24) and the treatment tool (9), and

   in that the rotary-action member (24) and the positioning coupling (46) are connected to the treatment tool (9) by means of a rotating and sliding coupling (26, 22; 22, 23) enabling the setting of the rotary position and the reciprocating motion of the treatment tool (9).
2. Head (1) for a medical or dental handpiece (2), comprising a casing (3), in particular an angled casing, in which a treatment tool (9) is supported so as to be displaceable back and forth along its central axis (9a) and rotatable,
   wherein the handpiece head (1) comprises an overspeed cut-out device which is effective between the casing (3) and the treatment tool (9), consisting of an overspeed coupling (46) with two coupling parts (14, 21) interacting with one another and disposed in or on the casing (3), one coupling part (14) being connected to the casing (3) and the other coupling part (21) being connected to the tool (9), the overspeed coupling (46) being connected to the treatment tool (9) by means of a sliding coupling (22, 23) enabling the reciprocating motion of the treatment tool (9),
   characterised in that

   the sliding coupling (22, 23) is disposed between the coupling part (21) connected to the treatment tool (9) and the treatment tool (9).
3. Handpiece head according to Claims 1 and 2,
   characterised in that

   the positioning coupling and the overspeed coupling are constituted by one and the same coupling (46) and both coupling parts (14, 21) of the common coupling (46) are parts of the handpiece head (1).
4. Handpiece head according to one of the preceding claims,
   characterised in that

   in the event of a predetermined torque acting on the tool (9) being exceeded in the engagement position (4 - 6) the positioning coupling and/or the overspeed coupling (46) is/are released or capable of being subjected to overpressure.
5. Handpiece head according to one of the preceding claims,
   characterised in that

   one coupling part (21) is movably supported in a guide and is pressurised into its engagement position by means of a spring force.
6. Handpiece head according to one of the preceding claims,
   characterised in that

   the coupling parts (14, 21) each comprise one or more coupling recesses (27) and coupling spigots (27b) engaging one another.
7. Handpiece head according to Claim 3,
   characterised in that

   the coupling surfaces (27a) which are preferably constituted by a tooth gearing are disposed divergently or obliquely between the coupling recesses (27) and the coupling spigots (27b).
8. Handpiece head according to one of the preceding claims,
   characterised in that

   the direction of motion of the mobile coupling part (21) is directed along the central axis (9a) of the treatment tool (9).
9. Handpiece head according to one of the preceding claims,
   characterised in that

   the positioning coupling and/or the overspeed coupling (46) are disposed concentrically in relation to the central axis (9a) of the treatment tool (9).
10. Handpiece head according to one of the preceding claims,
    characterised in that

    the coupling parts (14, 21) are axially juxtaposed annular parts which are capable of being brought into engagement with one another on their sides facing one another and the annular part disposed on the side facing away from the treatment tool is preferably the mobile coupling part (21).
11. Handpiece head according to one of the preceding claims,
    characterised in that

    the treatment tool (9) is capable of being fixed in a tool-receiving part (7) which is supported in the handpiece head (1) so as to be displaceable back and forth in the direction of the central axis (9a) of the tool (9) and is connected to the tool-receiving part (7) by means of the sliding coupling (22, 23; 22, 26).
12. Handpiece head according to one of the preceding claims,
    characterised in that

    one coupling part, in particular the mobile coupling part (21), is connected to the treatment tool (9) or to the tool-receiving part (7) by means of the sliding coupling (22, 23; 22, 26).
13. Handpiece head according to one of the preceding claims,
    characterised in that

    the positioning coupling and/or the overspeed coupling (46) are disposed in the end region of the tool (9) or of the tool-receiving part (7) on the tool side.
14. Handpiece head according to one of the preceding claims,
    characterised in that

    the rotary-action member (24) is accessible from the side of the handpiece head (1) remote from the tool, in particular it is disposed on this side preferably coaxially in relation to the tool (9).
15. Handpiece head according to one of the preceding claims,
    characterised in that

    the rotary-action member (24) is constituted by a disc, a wheel or a slewing ring.
16. Handpiece head according to one of the preceding claims,
    characterised in that

    a bearing remote from the tool for the tool-receiving part (7) is disposed in a bush (17) which is capable of being inserted into the casing head (3), in particular is capable of being screwed into the casing head.
17. Handpiece head according to one of the preceding claims,
    characterised in that

    the rotary-action member (24) is rotatably supported directly on the casing head (3) or on the bush (17), preferably on an end flange (19) of said bush.
18. Handpiece head according to one of the preceding claims,
    characterised in that

    the positioning coupling, the overspeed coupling or the common coupling (46) is effective between the tool-receiving part (7) and the casing head (3) or the bush (17) or a bearing ring (14).
19. Handpiece head according to one of the preceding claims,
    characterised in that

    an adjusting device (51) for the positioning coupling and/or the overspeed coupling (46) which is accessible from outside is disposed on the casing (3), with which device the positioning coupling and/or the overspeed coupling (46) is/are alternatively

    adjustable into an engagement position (Fig. 6) and a disengagement position (Fig. 7),

    or capable of being rigidly set in the engagement position,

    or with which device the initial tension of the positioning coupling and/or overspeed coupling (46) is capable of being increased, decreased or nullified entirely (Fig. 7).
20. Handpiece head according to Claim 19,
    characterised in that

    the adjusting device (51) is accessible from the side facing away from the tool (9), in particular it is disposed on this side preferably coaxially in relation to the central axis (9a) of the tool (9).
21. Handpiece head according to Claim 19 or 20,
    characterised in that

    the adjusting device (51) comprises an axially displaceable adjusting member (24a) and is in driving connection with the associated coupling part (21), preferably for the axial displacement thereof, or displaceable towards the coupling part (21).
22. Handpiece head according to one of Claims 19 to 21,
    characterised in that

    the adjusting member is a disc which is preferably seated on a flange (19a) capable of being screwed into the casing (3) of the handpiece head (1) and is axially displaceable thereon.
23. Handpiece head according to Claim 21 or 22,
    characterised in that

    locking elements, in particular releasable latching devices (52, 53), are assigned to the adjusting member (24a) with a view to releasable locking in its positions of adjustment, preferably with a spring element (54b) which is deflected into latching recesses (52a, 53a).
24. Handpiece head according to Claim 1 and one of Claims 19 to 23,
    characterised in that

    the rotary-action member (24) and the adjusting member (24a) are constituted by one and the same operating part, in particular by a rotating part, preferably a circular disc.

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